Europa,schesP_ MM II M M M I M Ml Mill M M I M J European Patent Office ... _. © Publication number: 0 283 961 B1 Office europeen* des.. brevets t © EUROPEAN PATENT SPECIFICATION © Date of publication of patent specification: 20.12.95 © Int. CI.6: C01 B 25/06, C01C 1/02, C01G 28/00, C01B 6/06, © Application number: 88104383.0 B01 D 53/28 @ Date of filing: 18.03.88 Process and composition for purifying arsine, phosphine, ammonia and inert gases to remove Lewis acid and oxidant impurities therefrom © Priority: 24.03.87 US 29632 © Proprietor: MILLIPORE INVESTMENT HOLD- INGS LIMITED @ Date of publication of application: 1013 Centre Road, 28.09.88 Bulletin 88/39 Suite 350 Wilmington, Delaware 19805 (US) © Publication of the grant of the patent: 20.12.95 Bulletin 95/51 @ Inventor: Tom, Glenn M. 2 Powder Horn Lane © Designated Contracting States: New Milford, Ct. 06776 (US) DE FR GB IT Inventor: Brown, Duncan W. 30 Cobblestone Place © References cited: Wilton, Ct. 06897 (US) EP-A- 0 179 969 US-A- 4 565 677 US-A- 4 659 552 © Representative: Schwan, Gerhard, Dipl.-lng. Elfenstrasse 32 PATENT ABSTRACTS OF JAPAN vol. 10, no. D-81739 Munchen (DE) 90 (C-337)(2147) 08 April 1986 00 CO Oi CO 00 CM Note: Within nine months from the publication of the mention of the grant of the European patent, any person ® may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition CL shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee LU has been paid (Art. 99(1) European patent convention). Rank Xerox (UK) Business Services (3. 10/3.09/3.3.3) EP 0 283 961 B1 Description BACKG ROU N D OF THE I N VEN JION 5 Field of jhejnventiqn This invention relates generally to a process and composition for removing Lewis acid and oxidant impurities from arsine, phosphine, ammonia, and inert gases. io Description of_the_ Related Art Arsine, phosphine, and ammonia are widely used in the semiconductor industry for the manufacture of microcircuitry devices, as source reagents for elemental arsenic, phosphorus, and nitrogen, respectively. In such applications, it is critical that the arsine, phosphine and ammonia source reagents be essentially 75 completely free of impurities such as water and oxygen. Such impurities, when introduced onto the semiconductor chip during its manufacture, tend to produce localized defects in the crystalline structure which may then propagate to produce an undesirable epitaxy, and render the chip deficient or even useless for its intended purpose. Arsine and phosphine are particularly difficult to purify, due to their extreme toxicity and hazardous 20 character, and the fact that they react detrimentally with many otherwise potentially useful scavengers to poison to active sorption sites of such materials. In addition, arsine and phosphine have a higher affinity for water than they do for inert impurities, e.g., nitrogen, which are less objectionable in the semiconductor manufacturing process. Although ammonia does not possess the toxicity and handling disadvantages of arsine and phosphine, 25 it nonetheless is a poison to many otherwise potentially useful scavengers, such as those commonly used in redox purification systems for removal of water and oxygen contaminants from other gases. Among the methods utilized in the prior art for removing water from ammonia are the use of moisture- sorptive molecular sieves. The difficulty of employing such method for production of high-purity ammonia for semiconductor applications is that ammonia is competitive with water for the adsorption sites on the 30 molecular sieves. As a result, it is not possible to obtain the necessary low residual water values, on the order of part-per-million concentrations of water in the effluent from the molecular sieve contacting step. Ammonia has also been dehydrated by sodium metal followed by distillation, although such methods are complex, costly, and entail the use of strong reducing agents. Arsine and phosphine have also been treated by molecular sieves to remove water but such treatment 35 in order to achieve high water removal efficiency requires that the molecular sieve contacting be carried out at low temperatures, e.g., on the order of about -20 degrees Centrigrade for arsine. This and other refrigeration-based water removal techniques involve high energy expenditure and operating costs, and therefore are not fully satisfactory. In addition, trimetal eutectics comprising indium and gallium components, and liquid at room tempera- 40 tures, have been employed for purifying arsine and phosphine of water impurity, but such dehydration method suffers the disadvantage that substantial amounts of oxide particles are generated in the treatment stream. Apart from arsine, phosphine, and ammonia, a variety of inert gases are employed in semiconductor manufacturing, for which extremely high purity is also required. As used herein, the term "inert gases" is 45 intended to be broadly construed as being inclusive of gases which may be unreactive in various semiconductor manufacturing operations, and are selected from the group consisting of one or more members of the group consisting of nitrogen, hydrogen, helium, argon, neon, xenon, silane, germane, and gaseous hydrocarbons (methane, ethane, ethylene, propane, propylene, etc.). Japanese Kokai Tokkyo Koho JP 60/222127 discloses the thermal decomposition of trimethyl aluminum 50 to deposit elemental aluminum on a glass substrate, e.g., glass beads, following which the aluminum coating is reacted with arsine to form a scavenger for water and oxygen. EP-A-0 179 969 and US-A-4,603,148 disclose a macroreticulate polymer scavenger for removing Lewis acid and oxidant impurities from inert fluids such as aliphatic hydrocarbons, olefins, and gases including nitrogen, argon, helium, xenon, hydrogen, carbon tetrafluoride, ammonia and silane, and a process for 55 purifying fluids containing Lewis acid and oxidant impurities by the use of such a scavenger. The macroreticulate polymer backbone of the scavenger has bonded thereto a plurality of metallated functional groups of the formula: 2 EP 0 283 961 B1 •At- ■C- I M where: Ar is an aromatic hydrocarbon radical of 1-3 rings; Ri and R2 are each independently hydrogen, C1- C12 alkyl, methylene-bridged benzophenone, methylene-bridged fluorenone, or alkali or alkaline earth metal salts of such benzophenone or fluorenone radicals; and M is lithium, potassium, sodium, alkyl magnesium, 10 or alkyl zinc, the alkyl substituents being C1-C12 alkyl. Within the pores of the macroreticulate polymer is a metallating agent selected from the group consisting of alkyl lithium, alkyl sodium, alkyl potassium, dialkyl magnesium, alkyl magnesium halide, dialkyl zinc, wherein the alkyl moiety is C1-C12 alkyl; alkali or alkaline earth metal salts of benzophenone; and alkali or alkaline earth metal salts of fluorenone. It is an object of the present invention to provide a highly efficient composition and process for 15 removing Lewis acid and oxidant impurities from arsine, phosphine, ammonia, and inert gases. It is another object of the invention to provide a composition and process of such type, which when employed to dry arsine, phosphine, ammonia, and inert gas streams, is capable of reducing the water content of the treated stream to levels on the order of 0.01 part per million by volume and less. Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure 20 and appended claims. SUMMARY OF THE INVENTION In one aspect, the invention relates to a process for purifying a gaseous mixture comprising (i) a 25 primary component selected from one or more members of the group consisting of arsine, phosphine, ammonia and gases selected from the group consisting of one or more members of the group consisting of nitrogen, hydrogen, helium, argon, neon, xenon, silane, germane, and gaseous hydrocarbons, and (ii) impurities selected from one or more members of the group consisting of Lewis acids and oxidants, to remove such impurities therefrom, comprising: 30 contacting the mixture with a scavenger including a support having associated therewith, but not covalently bonded thereto, a compound which in the presence of the mixture provides an anion which is reactive to effect the removal of the impurities, such compound being selected from the group consisting of one or more members of the group consisting of: (i) carbanion source compounds whose corresponding protonated carbanion compounds have a pKa 35 value of from about 22 to about 36; and (ii) anion source compounds formed by reaction of the aforementioned carbanion source compounds with the primary component of the mixture. said scavenger being devoid of metallated pendant functional groups. As used herein, "carbanion source compounds whose corresponding protonated carbanion compounds 40 have a pKa value of from about 22 to about 36" refers to compounds which in the presence of the impurity- containing mixture provide a carbanion which is directly or indirectly reactive to effect the removal of impurity constituents, i.e., the carbanion provided by such compound either itself reacts with the impurity species to remove same from the mixture, or else the carbanion provided by the compound reacts with a primary component of the mixture, viz., arsine, phosphine, or ammonia, to yield an anion source compound, 45 an arsenide, phosphenide, or amide compound, which in turn reacts with the impurity species to remove same from the mixture. It will be appreciated that when the primary component of the impurity-containing mixture is an inert gas, only the carbanion source compounds will be the impurity-removing compounds, i.e., the inert gas, since it is inert, will not react with the carbanion source compounds to form any anion source compounds. 50 The carbanion source compound thus comprises a cation and an associated carbanion moiety.